MAGNETISM AND ELECTRICITY. 



MAGNETS. 



Note. A desire to secure favorable atmospheric conditions for 

 experiments in frictional electricity has determined the order in 

 which the following branches of physics are taken up. In most 

 places in this country, the school-year begins with September. In 

 such cases, this chapter would probably be reached by January, 

 during which month the atmosphere is generally dry. Under other 

 circumstances, the consideration of these subjects would better be 

 omitted until sound, heat, and light have been studied. 



302. Natural Magnet. The mineral called load- 

 stone is the only known natural magnet. It is an ore of 

 iron, composed of iron and oxygen. // a piece of load- 

 stone be rolled in iron filings, some of the filings 

 luill cling to the loadstone when it is removed. 



303. Artificial Magnets. Artificial magnets are 



usually made of steel. They have 

 all the properties of natural mag- 

 nets, are more powerful and con- 

 venient. They are, therefore, pref- 

 erable for general use. The most 



common forms are the straight or bar magnet and the 

 horseshoe magnet. The first of these is a straight bar of 



FIG. 119. 



